The luminous-flame burner uses which type of air only?

The luminous-flame burner specifically utilizes secondary air, which plays a critical role in its operation. Secondary air is supplied to the burner to facilitate the combustion process and support the production of a luminous flame, characterized by its bright, visible glow.

In this type of burner, primary air is typically mixed with the fuel before combustion occurs, but it does not contribute to the visible luminous flame effect. The primary air is essential for mixing with the fuel at the burner inlet for efficient combustion, but the distinctive glowing characteristics of the flame depend largely on how secondary air is introduced into the combustion zone.

The concept of tertiary air is less relevant for luminous-flame burners, as it typically pertains to other types of combustion systems that aim to optimize combustion efficiency and reduce emissions by introducing additional air after the combustion process. Mixed air would refer to combinations of primary and secondary air but does not pinpoint the specific air type that creates the luminous effect in this burner design.

Thus, the correct identification of secondary air as the type used by the luminous-flame burner highlights its importance in creating the characteristic color and intensity of the flame.